The reason for using such few resources is that Physics is a teacher-oriented subject where self-studying new concepts is difficult and you often have to rely on your schoolteacher and their notes. That being said, self-studying can go a long way in learning the intricacies of each topic and what you can be tested on once you've learnt all the concepts.

In the last few days, I would advise reading the IB Physics v4 Questionbank for each topic to revise all the past papers. A quick way to solve all Questionbanks is to open the Questionbank on one half of the screen and the Answers on the other, read a question, and solve it mentally (for writing questions, either mentally recite for writing questions or make a note of the processes and formulas to use for calculation questions). Then you can compare your answer with the marking scheme, and highlight something you missed. This can help you to skim through the Questionbank quickly.

All the resources mentioned above can be found online on sites hosted by IB Alumni. Soft copies of the Oxford, Cambridge, and Pearsons book can also be found online. I would recommend choosing one publisher's book and sticking to it.

Studying for Astrophysics is not difficult, and once you put in the time commitment, you can easily score in the 7 band. Practicing past questions is the best way to prepare for the Astrophysics paper, but owing to the syllabus change in 2016, there aren't many practice questions for new Astro topics like Jean's criterion and expansionary models of the universe. The best way to prepare for these is to re-read the subject guide over and over to familiarise yourself with the new assessment statements, then look for online materials pertaining to the new topics. I also used the Tsokos Astrophysics book and read the content on new topics over and over.

One resource that is hard to procure online is any study material for Nature of Science (NoS). This is because it's very difficult to predict what might come for NoS questions. Here are the two online resources I used :